the right-of-way graded and used by the California Southern is still in use. Several structures built for or by the railroad, or in some cases their remains, can still be seen. Some of the buildings that remain are still in use in their primary purposes. The two ends of the former railroad are still in use as of 2013. The section between Barstow and Riverside through Cajon Pass, which includes the disputed crossing in Colton, remains one of the busiest rail freight corridors in the United States, seeing trains of BNSF Railway and Union Pacific Railroad as well as passenger service from Amtrak's daily Southwest Chief intercity train and commuter trains of Metrolink's IEOC Line. At Cajon the concrete pads that served as the foundations for the railroad's station facilities and water tanks there remain long after the buildings atop them were removed. The Santa Fe realigned the track at several places during the 20th century to straighten curves along Cajon Creek (between Cajon and San Bernardino), lower grades for eastbound trains with the 1913 addition of a separate track through what has come to be known as Sullivan's Curve, and to reduce some curvature and lower the pass's summit elevation by 50 ft (15 m). The maintenance shops in San Bernardino are still in use by BNSF Railway, although not to the extent that they were used in the 20th century. The San Bernardino station that was opened by the California Southern was destroyed by fire on November 16, 1916. It was replaced in 1918 by the Santa Fe with the current structure that now serves Metrolink's San Bernardino Line commuter trains on runs that terminate at Los Angeles Union Station as well as some IEOC Line trains to Oceanside. Until the introduction of weekend service on the 91 Line in July 2014, limited service from San Bernardino to Riverside was provided by some San Bernardino Line trains, and the Metrolink Riverside Line terminates at the Riverside station although it reaches the station via a more southerly route on the UP Los Angeles Subdivision. South of Riverside the track is still in place to Perris. This section has been rehabilitated to the Perris Valley Line, an extension of Metrolink 91 Line with service to stations at Hunter Park/UCR, Moreno Valley/March Air Reserve Base, Perris Downtown, and South Perris. Though the 91/PVL curves east south of downtown Perris to South